tbuckley/cabot-search huggingface dataset:
Abstract P3020: O-GlcNAc Transferase Regulates Vascular Smooth Muscle Cell Cycle Progression In Diabetes
Authors: Neha Bhavnani, Saugat Khanal, Amy Mathias, Jason Lallo, Shreya Gupta, Priya Raman
Journal: Circulation Research (2023)

Diabetic patients show increased proclivity for vascular smooth muscle cell (VSMC) migration and proliferation. Hyperglycemia, hallmark of diabetes, increases intracellular glucose signaling via O-linked N-acetylglucosamine transferase (OGT), a key regulator of protein O-GlcNAcylation. We previously showed that smooth muscle OGT (smOGT) deletion prevents hyperglycemia-induced atherosclerosis. Goal of this work was to interrogate the role of smOGT in VSMC cell cycle progression in diabetes. For this, we used conditional SMC-specific OGT knockout (smOGT KO ) and wild-type (smOGT WT ) mice generated via tamoxifen (tmx)-inducible VSMC-restricted Cre driver mice ( Itga8-CreER T2 ). Briefly, following tmx injection, 8-wks-old smOGT KO and smOGT WT mice were placed on Western diet feeding regimen for study duration. At 14-wks-age, mice were injected with 50mg/Kg/day streptozotocin i.p. once daily for 5 consecutive days. Mice were harvested at 16-18-wks-age and plasma and aortic tissues were collected for biochemical and molecular studies. Immunoblotting of aortic lysates revealed a significant decrease (59%) in OGT and O-GlcNAc expression, validating the smOGT KO mice. Loss of smOGT reduced (40%) CDK6 expression (regulator of G1-S phase cell cycle progression) concomitant to enhanced (62%) p21 Cip1 expression (cyclin-dependent kinase inhibitor) in aortic vessels from diabetic smOGT KO vs. smOGT WT mice. This was further accompanied with 69% attenuation in SRF expression (transcriptional regulator of SM proliferation) in diabetic smOGT KO vs. smOGT WT aortic vessels. Similar results were obtained with OGT loss-of-function studies in human coronary artery SMC (HCASMC) primary cultures under diabetic conditions in vitro . Briefly, control (siCtrl) and OGT siRNA (siOGT)-transfected HCASMC were treated with or without 25mM glucose+100μM PUGNAc for 48 hours. Immunoblotting revealed that reduced OGT-mediated O-GlcNAcylation in siOGT cells in a diabetic milieu significantly attenuated SRF expression coupled with augmented p21 Cip1 expression compared to diabetic siCtrl cells. Together, our results suggest a direct regulatory role of smooth muscle OGT in VSMC cell cycle progression in diabetes.
Abstract P1148: Glucocorticoid Receptor - Klf9 Axis Regulates Cardiomyocyte Metabolic Homeostasis
Authors: Chandni Thakkar, Saleena Alikunju, Wajiha Rizvi, Ali Abbas, Zhi Yang, Danish H Sayed
Journal: Circulation Research (2023)

Glucocorticoids (GCs) through activation of the Glucocorticoid receptor (GR) plays an essential role in cellular homeostasis during physiological variations and in response to stress. GC-GR signaling is involved in regulating several cellular processes including metabolism, circadian rhythm and inflammation for diurnal adaptations. Our genomic GR binding (ChIP) and transcriptome (RNAseq) data from Dexamethasone (Dex) treatment in cardiomyocytes show an early (1hr) differential regulation of mostly transcription factors, followed by sequential change in downstream signaling pathways (6-12hr). Here, we examine the role of an early direct target of GR in cardiomyocytes, Krüppel-like factor 9 (Klf9) in metabolic homeostasis. Our Klf9-ChIPseq identified 4100 genes with change in promoter Klf9 binding in response to Dex. Functional annotation of these genes lists metabolic pathway on the top of KEGG pathway, along with genes regulating transcription and survival. Interestingly, integration of GR and Klf9 data show overlapping targets (1181), suggesting that Klf9 could be serving as feedback regulator for these genes. Further, our transcriptome analysis of Dex treated cardiomyocytes with knockdown of Klf9 reveal differential regulation of 1777 genes (Dex+siKLf9 vs Dex+siLUC), of which a reversal in expression is seen in 1640 (92%) genes with siKlf9 vs. Dex. Conversely, only 137 (8%) genes show further dysregulation in expression with siKLf9 as Dex. Gene ontology of these 1640 genes show metabolic pathway on the top, including genes involved in glycolysis and oxidative phosphorylation. Conversely, mostly immuno-regulatory genes are among those 137 genes. Expectedly, knockdown of Klf9 in cardiomyocytes inhibits Dex induced increase in glycolysis and glycolytic capacity by 24%, and spare respiratory capacity by 50%, as measured by ECAR and OCR with glycolysis and mito stress tests, respectively. Thus, we conclude that cyclic, diurnal GC mediated GR activation, through Klf9 -dependent feedforward signaling plays a central role in maintaining cellular metabolic homeostasis. With hypertrophic stress a decrease in cardiac GR and dysregulated Klf9 signaling might result in metabolic crisis, contributing to mitochondrial and cardiac dysfunction
Abstract GS.09: Interleukin 13 Signaling To Macrophages Promotes Recovery After Myocardial Infarction In Mice
Authors: Santiago Alvarez-Argote, Caitlin Omeara
Journal: Circulation Research (2023)

Introduction: There is great interest in identifying signaling pathways that promote pro-reparative macrophage phenotypes in the heart. Considering the remarkable cardiac healing potential of neonatal mice, we employ this model to identify pro-reparative mechanisms that can be applied to promote cardiac repair in adults after myocardial infarction (MI). We show that IL13/IL4Rα signaling specifically on macrophages mediates neonatal heart regeneration and activation of this pathway in adult mice promotes cardiac functional recovery in post-MI. Results: We developed IL4Rα fl/fl ;CX3CR1 Cre mice (IL4Rα MacKO ) to delete IL4Rα specifically in macrophages. Neonatal IL4Rα MacKO and control mice were subjected to MI on postnatal day 1 (P1). Following injury, IL4Rα MacKO mice had significantly larger scars at 8 days post injury (dpi) and lower ejection fraction and capillary density at 21 dpi. Thus, macrophage IL4Rα expression is critical for cardiac functional recovery following injury in neonates. Using fluorescent reporter mice, we found that IL13, a ligand for IL4Rα, is produced almost exclusively by type 2 innate lymphoid cells in the neonatal heart. Interestingly, we didn’t find any cellular source of IL13 in the adult mouse heart. Considering the decline in cardiac production of IL13 from neonatal to adult stages, we postulated that reactivation of IL4Rα in the adult heart would improve cardiac healing post MI in adults. Indeed, daily IL13 administration significantly improved cardiac function post MI in adult mice, and this improvement was mediated entirely by IL4Rα expression on macrophages as IL4Rα MacKO mice showed no functional improvement with IL13 administration. Intriguingly, while IL13 administration to control mice improved cardiac function, administration to IL4Rα MacKO mice further exacerbated post MI mortality and scar size compared to animals receiving PBS, suggesting multiple cardiac cell types respond to IL13 resulting in beneficial or detrimental outcomes. Conclusions: Our data elucidates a strongly pro-reparative role for IL13 signaling directly to macrophages. While this signaling pathway is active in neonatal stages, we demonstrate that re-activation by IL13 administration is required to promote cardiac repair in adults.
Abstract P3202: The Branched Chain α-Ketoacid Dehydrogenase Kinase (BCKDK) Inhibitor BT2 Is A Mitochondrial Uncoupler
Authors: Aracely Acevedo, Anthony Jones, Ajit Divakaruni
Journal: Circulation Research (2023)

Elevated levels of branched-chain amino acids (BCAAs) are associated with cardiovascular and metabolic disease including heart failure, diabetes, and obesity. BCAAs are first transaminated into their respective branched-chain α-ketoacids (BCKAs) by the mitochondrial branched-chain amino-transaminase (BCAT m ). The pharmacological agent BT2 (dichloropheno[b]thiophene-2-carboxylic-acid) was designed to induce catabolism of BCAAs by inhibiting the branched-chain α-ketoacid dehydrogenase kinase (BCKDK). The function of BCKDK is to phosphorylate and therefore deactivate the branched-chain α-ketoacid dehydrogenase (BCKDH), an enzymatic complex that converts the BCKAs into their respective R-CoAs. Although it has been shown that BT2 protects from heart failure and metabolic disease in animal models, recent studies have suggested that its protective effects may originate from a mechanism independent of targeting BCAA oxidation. The objective of this study was to investigate alternative molecular mechanisms by which BT2 may confer cardioprotection and protect from metabolic disease. We hypothesized that BT2 is a mitochondrial uncoupler based on its chemical structure as a lipophilic weak acid. We demonstrate BT2 is a mitochondrial uncoupler using a combination of respirometry, membrane potential, and patch-clamp electrophysiology. BT2 has 20% of the potency of the chemical uncoupler 2,4-dinitrophenol (DNP). The data suggest BT2 may exert some of its cardioprotective effects and protection from metabolic disease via mitochondrial uncoupling.
Abstract P2067: Loss Of Cardiomyocyte β2 Spectrin Promotes Cardiac Dyad Dysfunction And Accelerated Heart Failure
Authors: Shane S Scott, Ethan Schwendeman, Anna Matzko, Jeffrey Tonniges, Neil Schwieterman, Mohamed Derbala, Sakima A Smith
Journal: Circulation Research (2023)

Background: The cardiac dyad is composed of the transverse-tubules, junctional sarcoplasmic reticulum (jSR), and its associated calcium (Ca 2+ ) release units, which are integral for cardiac excitation-contraction (E-C). Proper E-C coupling requires Ca 2+ influx via L-type Ca 2+ channels (LTCC) which triggers Ca 2+ release from adjacent ryanodine receptor 2 (RyR2) receptors located in jSR. Loss of the βII-spectrin scaffolding protein alters RyR2 localization; however, its contribution to cardiac dyad organization and E-C coupling remains unclear. Hypothesis: We hypothesized that βII-spectrin is required for cardiac dyad organization and proper cardiomyocyte calcium signaling. Methods: Cardiomyocyte-specific βII-spectrin knockout (βII-cKO) and control (βII-flox) mice were generated and hearts were harvested for immunoblotting, qRT-PCR, and transmission electron microscopy (TEM). Cardiomyocytes were isolated and stained using proximity ligation assay (PLA) and visualized by confocal microscopy. To assess heart response to pressure overload, control and βII-cKO mice were subjected to transaortic constriction surgery followed by treatment with or without, diltiazem and monitored by echocardiography, and electrocardiography. Results: Cardiac dyad structure and components are significantly altered in βII-cKO hearts. Ultrastructural analysis of βII-cKO hearts showed fragmented cardiac dyads, dilated jSR and reduced jSR contact with T-tubules. Quantitative RT-PCR and immunoblotting analysis revealed altered expression of dyad mRNAs and proteins. Preliminary PLA demonstrated reduced density of LTCC-RyR2 complexes. Furthermore, pressure-induced overload of βII-cKO hearts promoted accelerated heart failure (HF), which can be rescued by treatment with diltiazem. Conclusions: We demonstrate that βII-spectrin is required for cardiac dyad integrity, and that βII-spectrin-mediated HF can be attenuated by diltiazem.
Abstract P1151: Exploring The Role Of Bh3-like Motif Containing Cell Death Inducer In Cardiomyocyte Death: Insights From Human Failing Hearts And Ipsc-derived Cardiomyocytes
Authors: Praveen K Dubey, Sarojini Singh, Lei Ye, Steven pogwizd, Jianyi J Zhang, Prasanna Krishnamurthy
Journal: Circulation Research (2023)

Background: Cardiac cell death plays a critical role in the development and progression of heart failure. Identifying new molecular targets to limit cardiac cell death could improve patient lives. BLID (BH3-Like Motif-Containing Cell Death Inducer) is a member of the BCL family of proapoptotic genes containing a BH3-like motif that induces cell death. Previous studies have shown that in many human cancers, downregulation of BLID is associated with tumor progression, while overexpression promotes cell death through a caspase-dependent mechanism. However, its role in cardiomyocyte death under various stress conditions is unknown. Methods and Results: Our RNAseq data from human failing and non-failing hearts revealed that mRNA expression of the BLID gene was significantly upregulated in human heart failure. We further validated our RNAseq findings by measuring the expression of BLID in RNA and protein isolated from the same set of human failing and non-failing hearts. As expected, the expression of BLID was significantly upregulated at both the mRNA and protein levels in human failing hearts compared to non-failing hearts. Furthermore, in cultured human cardiomyocytes (AC16 cells) and iPSC-derived cardiomyocytes exposed to stressors (such as hypoxia or H 2 O 2 ) for 2 hours, we observed a significant upregulation of BLID expression at both the mRNA and protein levels. We also overexpressed human BLID protein in human cardiomyocytes, leading to cardiomyocyte death. To determine their localization, we fractionated the overexpressed BLID proteins into cytoplasmic, nuclear, and mitochondrial fractions. We found that BLID was localized in the cytoplasm, nucleus, and mitochondria, with higher levels in the nucleus and mitochondria. These findings suggest that increased expression of BLID in failing human hearts may lead to cardiomyocyte death. Conclusion: Our data suggest that increased expression of BLID in human heart failure may be a key molecule that drives cardiomyocyte death. Inhibiting its expression during heart failure could mitigate cardiomyocyte death and improve cardiomyocyte function and survival.
Abstract P2119: Effect Of PCI On QTd And QT Interval Compared To Control/other Treatments For Myocardial Infarction
Authors: Advait Vasavada, Manisha Jain, Dakshin Meenashi Sundaram, Thulasi Ram Gudi, Kamran Mahfooz, Radhika Kotak, Ganeev Singh
Journal: Circulation Research (2023)

Background: QT dispersion measurement is a potential risk stratification tool but is a conflict in the literature on how PCI and other procedures affect it. We aimed to compare PCI with other procedures like Streptokinase, PCI plus thrombectomy, and coronary artery bypass graft (CABG) on QT interval. Methods: We conducted a systematic review and meta-analysis on the association between PCI and QTd through a literature search in three electronic databases, Science Direct, PubMed, and Google Scholar, for empirical studies published in English. Random effects model was used. Results: Eleven studies were found in total. We found significant differences in QTc between pre and post PCI and a significant reduction in QTc across all the studies (SMD 2.57, 95% CI 1.22 to 3.92; p&lt;0.05). Five studies compared the efficacy of PCI and control (other procedures) in reducing QTd after 24 hours of treatment procedures. The mean change from baseline in QTd is more significant in the PCI group (post-PCI) compared to the control group, although there is no statistically significant difference between the two groups (SMD -0.30, 95% CI -1.25 to 0.65; I2 = 96%). A significant reduction in QTd corresponding to a statistically significant difference between QTd prior and post-PCI intervention for QTd at 2hrs, 24hrs, and 2-7 days, was found. The estimated overall effect measure reveals statistical significance (SMD 1.18, 95% CI 0.70 to 1.65; P &lt; 0.05). Conclusion: QTd difference was significant post-PCI. Future studies on evaluating it as a predictor to various outcomes could illustrate it's benefit in clinical practise.
Abstract P2089: Myocardial Long Non-Coding RNAs Expression Signatures In Heart Failure With Preserved Ejection Fraction
Authors: Alina Guo, Edwin Yoo, Hildur Knuttsdottir, David A Kass, Kavita Sharma, Virginia S Hahn
Journal: Circulation Research (2023)

Heart failure with preserved ejection fraction (HFpEF) accounts for greater than half of all HF cases and has 5 year mortality rates on par with HF with reduced ejection fraction (HFrEF). Unlike HFrEF, however, HFpEF patients have limited therapeutic options. Improved understanding of myocardial epigenetics are needed to develop novel therapeutics. We have previously conducted myocardial transcriptomics in HFpEF and found several thousand differentially expressed genes between HFpEF vs Controls. Targeting a single gene or pathway will likely not address the many abnormalities seen in HFpEF, highlighting the need for epigenetic approaches. Long non-coding RNAs (lncRNAs) exert epigenetic control over large numbers of transcripts and represent potential therapeutic targets in HFpEF.We measured lncRNA expression from myocardial tissue from HFpEF (n=41), HFrEF (n=30), and control (CON, n=24). Agnostic principal component and hierarchical gene clustering analyses separated HFpEF, HFrEF and CON with minimal overlap. LncRNA’s differentially expressed in HFpEF were predicted to control pathways related to neurotransmitter release, cytoskeleton, and muscle cell development. Three lncRNA-derived HFpEF subgroups were identified with distinct clinical correlates and clinical outcomes, and a subset of these predicted a poor prognosis. Differential expression analysis using DESeq2 revealed 95 upregulated and 342 downregulated lncRNAs.Our findings suggest that HFpEF has a lncRNA profile distinct from HFrEF and controls, highlighting potential epigenetic therapeutic targets for HFpEF.
Abstract P3174: Loss Of Hmgcs2-mediated Ketogenesis Accelerates Cardiac Aging
Authors: Yi-Chan Lee, Yuan-Yuan Cheng, Hsin-Yuan Chien, Shu-Chian Ruan, Po-Ju Lin, Patrick C Hsieh
Journal: Circulation Research (2023)

Introduction: We have previously reported that the ketogenic enzyme HMGCS2 regulates metabolic changes to ameliorate cardiac damage by promoting adult cardiomyocyte dedifferentiation and proliferation after myocardial infarction (Cheng et al. Circulation , 2022). Intriguingly, ketogenic diet has been shown to prolong the lifespan of aged mice. However, whether the loss of HMGCS2 links to cardiac aging remains unclear. Hypothesis: We tested if loss of HMGCS2 results in metabolic change and heart dysfunction and leads to premature cardiac aging. Methods and Results: Conventional HMGCS2 knock-out (KO) mice were generated by inserting loxP sites flanking exon 2 of HMGCS2 to eliminate HMGCS2 protein production. HMGCS2 expression and β-hydroxybutyrate production were eliminated in the livers and hearts in HMGCS2 KO mice. Echocardiographic analysis and intraventricular catheterization did not display heart functional differences between wild-type and HMGCS2 KO mice at 3-month-old. However, growing with age, HMGCS2 KO mice revealed a declining survival rate, accompanied by worse diastolic and systolic functions including reduced left ventricle ejection fraction, myocardial performance index, fractional shortening, stroke volume, end-diastolic dimension, end-systolic dimension, isovolumic relaxation time, and left ventricular diastolic time constant (Tau) in HMGCS2 KO mice at 12-month-old. Histological analyses also exhibited aging-related phenotypes in the HMGCS2 KO heart at 12-month-old, including cardiac hypertrophy and fibrosis. Furthermore, mitochondrial analyses indicated mitochondrial impairments of function and structure. Conclusion: These results suggest that loss of HMGCS2 accelerates cardiac aging with declining cardiac and mitochondrial function.
Abstract P3129: Strain-induced Cardiac Arrhythmias Caused By A Noonan Syndrome Mutation In Raf1 Can Be Suppressed By Modulation Of The Ras-mapk Pathway <i>In Vitro</i>
Authors: Fereshteh Haghighi, Leonie Boehmker, Aiste Liutkute, Karolin Kleemann, Alexandra V. Busley, Jan P. Pietras, Funsho E. Fakaude, Fitzwilliam Seibertz, Tony Rubio, Ingo Kutschka, Martin Zenker, Niels Voigt, Lukas Cyganek, George Kensah
Journal: Circulation Research (2023)

The gain of function mutation RAF1 S257L/+ , accounting for more than 50% of Noonan syndrome (NS) cases, results in a hyperactive RAS-MAPK pathway. Individuals suffer from myocardial dysfunction including electrophysiological abnormalities. Resulting arrhythmias may be potentially life-threatening, if sinus rhythm is not restored expeditiously. Intensive research has provided insights into structural anomalies. However, electrophysiological abnormalities contributing to arrhythmia initiation and maintenance in affected NS patients have not yet been investigated in-depth.To delineate the role of RAF1 S257L/+ in cardiac rhythm disturbance in vitro , we used cardiomyocytes differentiated from NS patient-derived (RAF1 S257L/+ ) and isogenic gene-corrected (RAF1 corr/+ ) iPS cells to generate 3D bioartificial cardiac tissues (BCTs). In a custom-made bioreactor system, we applied mechanical preload to BCTs to resemble an in vivo physiological stress condition. Here, in RAF1 S257L/+ BCTs, we observed a high susceptibility to arrhythmias compared to RAF1 corr/+ myocardium. This abnormality came alongside with a severely stiffened myocardium, and an impaired myocardial relaxation, pointing towards a diastolic disfunction. Electrophysiological analysis revealed a potentially arrhythmogenic shortening in action potential duration in RAF1 S257L/+ BCTs. Furthermore, the presence of spontaneous ectopic foci resulted in unstable excitation patterns. Long-term modulation of the hyperactive RAS-MAPK pathway by treatment with a MEK inhibitor, significantly reduced these arrhythmogenic parameters accompanied with a normalization of RAF1 S257L/+ BCT compliance, eventually stabilizing beating rhythm significantly.For the first time, our study provides an in-depth characterization of the RAF1 S257L/+ -associated arrhythmogenic phenotype in vitro . Shortened action potential durations, instable pace maker regions and a stiffened myocardium may contribute to the initiation and maintenance of severe cardiac rhythm anomalies. Moreover, we successfully rescued this distinct phenotype by pharmacological intervention. Our findings may have implications for future preventive treatment strategies for NS patients.